For example, a patent document 1 discloses a conventional non-contact electricity supply device including a power-supply-side coil, a power-receiving-side coil, a power-supply-side capacitor for a resonant circuit, and a power-supply-side filter circuit.
The non-contact electricity supply device includes a primary winding and a secondary winding. The non-contact electricity supply device further includes a capacitor for a resonant circuit and a filter circuit.
The primary winding is an element supplied with an alternating current from a high frequency AC power source to produce an alternating magnetic flux. The secondary winding is an element interlinked with the alternating magnetic flux, which is produced by the primary winding, to produce an alternating current. The capacitor is an element, which configures a resonant circuit with the primary winding. The capacitor is connected in parallel with the primary winding. The filter circuit removes a predetermined frequency component, which is included in an alternating current supplied from the high frequency AC power source. The filter circuit is configured with a coil and a capacitor, which are connected in series with each other. The filter circuit is connected between the high frequency AC power source and the primary winding.
A circuit, which is configured with the filter circuit, the capacitor, and the primary winding, has an impedance having a frequency characteristic including one maximum point and two minimum points. One of the two minimum point is caused by a resonance of a circuit, which is configured with the filter circuit and the primary winding. The one of the two minimum points is formed on the low frequency side relative to a frequency of the maximum point. The other of the two minimum points is caused by a resonance of a circuit, which is configured with the filter circuit and the capacitor. The other minimum point is formed on a high frequency side relative to the frequency of the maximum point.
The high frequency AC power source supplies an alternating current in a rectangular waveform. Therefore, the alternating current supplied from the high frequency AC power source includes a frequency component of a fundamental wave and odd-order harmonics components of the fundamental wave. In general, the frequency of the fundamental wave of the alternating current supplied from the high frequency AC power source is set at a frequency close to the maximum point to suppress an electric current to be supplied.